Is one torque arm enough?

[keysersoze310]

So I tried removing my rear wheel a few days ago and to my surprise, one of my Doctorbass torque arms fell off! Yes, I used the DP420, but my alignment wasn't particularly good on the one that fell off.

Anyways, while I rethink my torque arm situation, is it safe to ride my bike with only one torque arm at low power (<2kw) ? This would of course be without regen.

[Ykick]

I'm assuming direct drive since you mentioned no regen? I run 9C DD around 2kW with one thin AmpedBikes torque arm secured with sheet steel clamp. No regen and 3k miles later my aluminum dropouts looked absolutely perfect last time 'had the wheel off. No evidence it's even been needed yet. I don't know if I'd trust my setup to a geared hub motor at that power level but for 2807 in 26" wheel, I'm not pulling any wheelies and single torque arm is plenty.

You're probably okay although if one arm came loose the installation of both could be compromised and lacking structural integrity?

[ZOMGVTEK]

I had over 800 miles with a GM at 8kW without any torque arms. Just standard steel dropouts.

I eventually made a single sided torque arm once regen started killing my dropouts. The axle still wiggled its way loose fairly quickly, so I'm not using regen on that bike anymore. This was even with nordlock washers, and tightly shimmed dropouts with no play.

Bottom line, is a properly installed motor appears to be fine without any torque arms. Two friends bikes have no torque arms and GM's at 8kW. Never had a problem.

Long term, it's a good idea to have double sided torque arms. If you use regen, its basically mandatory. One side is better than none, but sloppy.

[dogman]

One good torque arm can be enough. My dirt bike has a superb pinch dropout, but only on one side. At some point, I expect I'll crush or twist an axle, as it's on the wire side. Good tight nut on the other side. A winter riding 3000w did no harm.

The operative word here is good. If your other glued on torque arm pops, you'll of course have no torque arm, just a hefty washer.

[keysersoze310]

Thanks, I'm pretty sure that the torque arm that is still attatched is fine. The one that fell off looked sketchy from the get go, but I was still surprised because I thought DP420 was nearly indestructible.

I'll stick with one torque arm for now while I try to figure out a good torque arm setup that can use regen without my crystalyte axle rocking.

[ZOMGVTEK]

If the DP420 fell off, it must have not adhered. It's probably not the adhesives fault. It's not a mechanical bond, so you need to be absolutely sure BOTH surfaces are clean. Sand them a bit rough, and wipe the surfaces with a solvent, it should hold well. Cure it at higher than ambient temps, with pressure, for best results.

[biohazardman]

I have run both of my electrics with only one arm. Total of 9K+ between the two and never had a problem with either at 1200-2500W+. Just keep an eye on the one thats left and the nuts that hold things together and you should be fine fer awhile.

[Doctorbass]

If the DP420 fell off, it must have not adhered. It's probably not the adhesives fault. It's not a mechanical bond, so you need to be absolutely sure BOTH surfaces are clean. Sand them a bit rough, and wipe the surfaces with a solvent, it should hold well. Cure it at higher than ambient temps, with pressure, for best results.

+1

Doc

[FastDemise]

Funny enough last weekend I found out I had the same problem with my Doc arms using DP420. Changed a flat tire and noticed it laying on the ground. I used vice grips to apply tight pressure and left it in front of 1500w heater to cure.

Did you just apply to the face of the torque arms? I applied to the inside and a liberal amount on the circumference to give a nice smooth look and help hold it. My guess is my arm was just not quite aligned right and my constant throttle and regen did it's damage.

[Spacey]

You have to Dremel/sand the frame part a lot. I scraped with a sharp screwdriver as well on the frame and also the torque arm to give a good surface for the DP420 to stick. Dremel the torque arm after you have cleaned it as well. Otherwise you will not get a good seal.

Mine is indestructible.

[keysersoze310]

Tried pulling the other side off and... pop goes the torque arm.

I even was able to pull out the derailleur hanger than I epoxied in. In other words, my torque arm install was a complete and utter failure. Thank god my stinky's dropouts are apparently pretty strong on their own.

I'm honestly not sure where I went wrong. I followed all of the directions listed above minus the dremel to rough them up, but I did get them rough with a metal file instead. Maybe I should have cured at an even higher temp for a few more hours... oh well.

I think I'm gonna go with the new ebikes.ca torque arms this second time around. They look strong and idiot proof. DP420 and I are apparently not compatible.

[Kingfish]

I use two for each wheel, one on each side. Once, I even had three torque arms for one wheel, but that was to make up for the deficiency of design. The best torque arms were the ones custom-made to fit. I made my own for the front and they worked like a champ. Farfle made one for me on the rear and it has been awesome. Can’t go wrong with dual protection.

~KF

[izeman]

If the DP420 fell off, it must have not adhered. It's probably not the adhesives fault. It's not a mechanical bond, so you need to be absolutely sure BOTH surfaces are clean. Sand them a bit rough, and wipe the surfaces with a solvent, it should hold well. Cure it at higher than ambient temps, with pressure, for best results.

would you remove paint before? or just sand the torque arm/plate and sand the paint a bit and glue them together? i have no idea how strong the paint sticks to the metal.

[ZOMGVTEK]

If the DP420 fell off, it must have not adhered. It's probably not the adhesives fault. It's not a mechanical bond, so you need to be absolutely sure BOTH surfaces are clean. Sand them a bit rough, and wipe the surfaces with a solvent, it should hold well. Cure it at higher than ambient temps, with pressure, for best results.

would you remove paint before? or just sand the torque arm/plate and sand the paint a bit and glue them together? i have no idea how strong the paint sticks to the metal.

You ABSOLUTELY have to remove the paint. The torque arms need to be metal on metal, with extremely clean and flat surfaces. A little rough texture is perfectly fine, but the torque arm must be flat against the bikes dropouts with sufficient exposed surface area.

If you sand the paint and adhere it to that, your dropouts are as strong as the paint. Paint isnt very strong.

If you're concerned, put a bolt through it, and weld the circumference. If it's not stronger than the stock dropouts, whats the point?

[cal3thousand]

If the DP420 fell off, it must have not adhered. It's probably not the adhesives fault. It's not a mechanical bond, so you need to be absolutely sure BOTH surfaces are clean. Sand them a bit rough, and wipe the surfaces with a solvent, it should hold well. Cure it at higher than ambient temps, with pressure, for best results.

would you remove paint before? or just sand the torque arm/plate and sand the paint a bit and glue them together? i have no idea how strong the paint sticks to the metal.

It is only as strong as the weakest link. So your installation on paint is only as strong as the paint's bond to the metal

[John in CR]

Is anyone actually surprised that this has started happening?

[auraslip]

Not really. The instructions weren't really clear in the thread. Maybe an install guide would be nice.

But just to be clear - you roughed up the drop out with a file. Did you also rough up the torque arm as well? Mind were covered with some sort of corrosion or something. Did you use a solvent? Did you apply pressure as it was curing?

I haven't done the math, but 4200 psi is an awful lot of shear strength. If they're installed good, they should hold. But I haven't done the math. Has anyone?

[keysersoze310]

But just to be clear - you roughed up the drop out with a file

Yes

Did you also rough up the torque arm as well?

Yes

Mind were covered with some sort of corrosion or something.

Mine were too, spent quite a while using my metal file to get rid of all the corrosion on the side I epoxied

Did you use a solvent?

Just cleaned it with alchohol

Did you apply pressure as it was curing?

Yep, clamped it down hard

[izeman]

another thought: maybe you bought a 'fake' product? nowadays there are piracy products everywhere. could have happened here as well. even pros can't tell the good from the bad stuff.

[auraslip]

Well this sucks. Now that I'll need to to drill through it, this drop out has ended up costing me twice as much as making my own.

[psycholist]

keysersoze310, You had a problem with a very loose fitting axle, resulting in a lot of rocking play in the torque arm and loosening of the axle nuts.
Did you ever resolve this issue? If you continued to ride in this state, something is bound to fail.
The integrity of the doctorbass torque arms require that the axle nuts be tight as well as a snug fit in the (torque arm) dropouts.
What might have occured here, is that you continued to ride with this condition and the loose axle nuts, accompanied by the constant rocking, caused the system to fail at it's weakest link...The epoxy bond.

I'm not implying that you did this. Just a possible scenario

[auraslip]

i'd like to think john for making me paranoid. LOL.
What happened was me drilling out the anti-crack hole. I guess it got warm and weakened and the torque from the drill popped it off. You can debate this all you want. I don't think I got it too hot.


Here is the solution I'm working on. Huge pain ;(

[auraslip]

Think I may have found our problem -> http://www.alibaba.com/trade/search?Cou ... cotch+weld

I got mine off ebay.

I've contacted the seller as well as 3m.

[keysersoze310]

keysersoze310, You had a problem with a very loose fitting axle, resulting in a lot of rocking play in the torque arm and loosening of the axle nuts.
Did you ever resolve this issue? If you continued to ride in this state, something is bound to fail.
The integrity of the doctorbass torque arms require that the axle nuts be tight as well as a snug fit in the (torque arm) dropouts.
What might have occured here, is that you continued to ride with this condition and the loose axle nuts, accompanied by the constant rocking, caused the system to fail at it's weakest link...The epoxy bond.

I'm not implying that you did this. Just a possible scenario

You are correct I had a rocking issue, but that was due to regen. My solution was... just don't use regen. I've only tested it out on low regen a couple of times like in the video I posted, so that wouldn't be nearly enough to cause this problem. The axle nuts were always kept very tight with nord lock washers.

@aura
Bummer. First off, I think you might have used the wrong epoxy? Its the black DP-420 that has the highest strength I believe, though the off white is probably strong enough as well.

I bought my epoxy on ebay as well... I think you might be on to something here. For the record, I'd stay away from ebay seller 9835tanzy just to be safe.

[izeman]

.. I guess it got warm and weakened and the torque from the drill popped it off. You can debate this all you want. I don't think I got it too hot.

drilling a hole with a not 100% good drill can make the plate very hot. and heat is the only way to remove epoxy. and once it got hot it's like dried jewing gum. can you pry the remaining epoxy off with a screw driver easily? if it falls of in small crumbles than you know it got too hot.
this must not be mixed up with applying heat while drying of the epoxy. there are some types that need heat to become harder. other type will stay like glue one heat is applied and will never dry.